WASHINGTON, June 15 (Reuters) - The U.S. military is providing intensified security for U.S. diplomatic facilities in Baghdad, the Pentagon said on Sunday, as the Iraqi government sought to repel a stunning advance by Islamist militants who have seized several Iraqi cities.

"A small number of (Defense Department) personnel are augmenting State Department security assets in Baghdad to help ensure the safety of our facilities," Pentagon spokesman Rear Admiral John Kirby said in a statement.

Earlier on Sunday, the State Department said it would move some workers out of the giant U.S. Embassy in Baghdad to other U.S. diplomatic facilities inside and outside of Iraq.

Kirby said the movement of U.S. personnel would take place aboard commercial, charter or State Department aircraft. "The U.S. military has airlift assets at the ready should State Department request them," he said. (Reporting by Missy Ryan; Editing by Peter Cooney)